Question

tinh gia tri bieu thuc :B=1.2+2.3+3.4+...+2010.2011

Answer 1

3B = 1.2.3 + 2.3.(4-1) + ... +2010.2011.(2012-2009)

3B = 1.2.3 + 2.3.4 - 1.2.3 + ..... +2010.2011.2012-2009.2010.2011

3B = 2010.2011.2012

B = 2010.2011.2012:3

B = 2710908440

Answer 2

3B = 1.2.3 + 2.3.(4-1) + ... +2010.2011.(2012-2009)

3B = 1.2.3 + 2.3.4 - 1.2.3 + ..... +2010.2011.2012-2009.2010.2011

3B = 2010.2011.2012

B = 2010.2011.2012:3

B = 2710908440